The benefits of strong abdominal muscles have long been recognized by sports and physical medicine professionals as well as by the average person. One particular advantage of strong abdominal muscles is the prevention and reduction of associated lower back problems. Traditional methods of exercising the abdominal muscles are not only largely ineffective, but exacerbate most lower back injuries.
The most common exercise for loading the abdominal muscles is trunk flexion, traditionally achieved using the well known sit-up exercise. The sit-up involves the user lying on their back, knees bent and toes hooked under a solid object for stabilization and then raising their torso until they are sitting up. Commonly, several repetitions of the sit-up exercise are performed. Alternatively, a sit-up can be performed using only the weight of the legs for stabilization.
Traditional abdominal exercises (sit-ups) result in trunk flexion being performed by the hip flexor muscles, the same muscles used to raise the knees when walking or stair climbing. The drawback with the traditional sit-up is that the desired motion of the exercise, trunk flexion, is not effected by contraction of the abdominal muscles.
The hip flexor muscles are attached to the pelvic girdle and when they contract a torque is produced about the hip joint. This torque causes the pelvis to tilt forward and flex the trunk. In this position, the lower back is unstable and the resulting shear forces applied to the vertebra cause undesirable stress on the lower back which can cause injury over time. Isometric contraction refers to a type of muscle contraction where the muscles are loaded but no motion occurs (an effect similar to pushing against an immovable object). If sufficiently strong, isometric contraction of the abdominal muscles tends to offset these shear forces placed on the veterbra, thereby stabilizing the lower back.
Accordingly, the principal object of this invention is to provide a means of stabilizing the body during a trunk flexion abdominal exercise in a manner that does not permit the hip flexor muscles to contract, thereby isolating the desired abdominal muscle contraction. Further objects of the invention include providing a means to cause the muscles associated with knee flexion and hip extension to contract, thereby forcing the hip flexors to relax. This helps to stabilize the pelvis (i.e. preventing pelvic tilt) and stabilize the lumbar region of the lower back during trunk flexion and typical upper body weight training exercises.